Presently available imaging diagnostic apparatus for capturing fluoroscopic images of patients include CT scanners, MRI apparatus, PET apparatus, ultrasonic diagnostic apparatus, CT angiography apparatus, MR angiography apparatus, and ultrasonograph. When such an imaging diagnostic apparatus is used to capture a fluoroscopic image of a patient, it is occasionally practiced to inject a liquid such as a contrast media or a physiological saline into the patient. A liquid injector for automatically injecting a liquid into a patient has been commercially available.
Such a liquid injector has a drive motor and a slider mechanism and the like, and employs a liquid syringe that is removably mounted. The liquid syringe comprises a cylinder member and a piston member slidably inserted in the cylinder member. The cylinder member is filled with a liquid such as a contrast media or a physiological saline to be injected into the patient.
The liquid syringe is connected to the patient by an extension tube and set on an injection performing means. The injection performing means individually holds the piston member and the cylinder member and moves them relatively to each other for injecting a liquid, typically a contrast media, from the liquid syringe into the patient.
The operator determines the rate at which the contrast media is to be injected and the total quantity of the contrast media to be injected, in view of various conditions, and then enters numerical data representing the rate and total quantity into the liquid injector. Based on the entered numerical data, the liquid injector injects the contrast media into the patient at the rate and in the quantity represented by the entered numerical data. The injected contrast media changes the image contrast of the patient, allowing the imaging diagnostic apparatus to capture a good fluoroscopic image of the patient.
Some liquid injectors are capable of injecting a physiological saline as well as a contrast media into the patient. For operating such a liquid injector, the operator enters, if desired, an instruction to inject the physiological saline following the completion of the injection of the contrast media, together with data representing the rate at which the physiological saline is to be injected and the total quantity of the physiological saline to be injected, into the liquid injector.
Based on the entered data, the liquid injector first injects the contrast media and then automatically injects the physiological saline after the contrast media has been injected. The subsequently injected physiological saline pushes the previously injected contrast media, reducing the consumption of the contrast media, and also reduces artifacts in the captured image.
Liquid injectors of the type described above have been devised and applied for patent by the applicant of the present application (see, for example, patent documents 1, 2 below).
The above liquid injector is capable of injecting a contrast media into the patient in order to change the image contrast of the patient to a state which allows the imaging diagnostic apparatus to capture a good fluoroscopic image of the patient.
When a contrast media for CT was actually injected into a patient by the liquid injector and a time-dependent change in the CT value, which represents the image contrast, was measured, it was found that even if the contrast media was injected at a constant rate, the CT value was not constant, but rose nonlinearly and then fell, and remained at an optimum level for a very short period of time.
Therefore, the conventional liquid injector which injects a contrast media at a constant rate that is represented by entered numerical data fails to provide optimum-imaging conditions in an imaging diagnostic apparatus combined therewith. For solving the above problem, it is necessary to change, with time, the rate at which the contrast media is injected. For example, it is known in the art to divide one cycle of liquid injection into a plurality of phases and set numerical values of a liquid injection rate and a liquid injection time for each of the phases.
However, in the liquid injector described above, when the operator enters numerical data representing injection condition such as the injection rate with a numeric keypad, the entered numerical data is only displayed as text data, and thus it is difficult for the operator to understand intuitively the injection condition from that displayed data. Therefore, the operation is complicated and is not easy for an unskilled operator, and entry of inappropriate numerical values cannot be prevented.
To solve the abovementioned problem, the present applicant has devised a liquid injector in which an operator enters injection conditions including a relationship between an injection time period and an injection rate to a touch panel and the entered injection condition is displayed on the touch panel to control the operation of liquid injection in real time in accordance with the injection condition, and has applied it as Japanese patent application No. 2002-099928 and Japanese patent application No. 2003-098057.
However, such detailed entries and control may not be required in the actual medical environment, and simpler input actions and displays may be desired. In addition, the operator can easily understand instinctively the injection condition as described above, but the numerical values of the injection condition is difficult to review quickly.